Howard installing solar cells at sewage treatment plant

Timothy B. Wheeler, The Baltimore Sun

Solar power is going everywhere these days — homes, businesses, schools, even sewage plants.

Howard County is beginning work this week installing about 740 photovoltaic panels at its Little Patuxent Water Reclamation Plant in Savage. The $1.5 million project will generate a fraction of the power needed by Maryland's fifth largest wastewater treatment plant. Its chief purpose, however, according to County Executive Ken Ulman, is to offset carbon emissions from big new diesel generators being installed to prevent sewage spills like the massive one triggered by Superstorm Sandy last year.

Nearly 20 million gallons of diluted but untreated effluent poured into the Little Patuxent River in October 2012 after storm-felled trees and branches knocked out power to the treatment plant. Ulman said he recalls with chagrin seeing the spill make national cable TV news.

"We vowed that it would never happen again," he said. After studying various options, officials decided the most reliable fail-safe for the treatment plant would be diesel generators, which are projected to cost $6.6 million. Then, at Ulman's urging, the county sought a way to mitigate the environmental impact of having to test the backup diesel burners weekly, as well as the instances when they are actually used — expected to be once or twice a year when storms knock out power.

Officials say the solar panels will more than make up for the carbon dioxide emitted by the generators. The 217 kilowatt-hours of electricity the array will generate when the sun is shining also should shave an estimated $22,800 from the plant's power bill for the year.

That won't come close to covering the total tab; the plant typically gobbles up many times that amount of electricity daily treating 21 million gallons of sewage, according to Steve Gerwin, the county's utilities bureau chief.

The county has applied for a state grant to help defray the combined $8.1 million cost of the solar and diesel installations.

"It's a big chunk of change to spend for something that happens every couple years," Gerwin said of preventing storm-related outages. "But it seems like it's happening more often."

State help or not, Ulman said the county can cover the costs without having to raise utility rates.

Howard is the latest community in Maryland and across the nation to turn to the sun to help treat wastewater. Baltimore installed a 1-megawatt, ground-mounted solar system at its Back River treatment plant last year, and earlier this month, the Washington Suburban Sanitary Commission showed off two 2-megawatt arrays of nearly 8,500 panels each at two of its sewage plants in Upper Marlboro and Germantown. Small plants on the Eastern Shore also have solar installations.

Space constraints limited the size of the solar array at the Little Patuxent plant, said Karen Galindo-White of Energy Systems Group, a private company helping the county. Even so, two new carports will be built at the facility to provide enough rooftops for the 15,000 square feet of panels.